Normally I defer to your wisdom, but a few points he

Peter Bennett wrote:
On 23 Jun 2005 08:02:14 -0700, wrote:
....


Do they have a "warm-up" time?

The three models I've used had a 90 second warm-up. They also have a
"standby" mode that turns off the transmitter, but leaves the
magnetron warm.


Note that magnetron life (which is a finite resource) is not used up
by standby time.



Do you use it continously?


I usually do. New users should certainly use the radar in good
visibility until they are confident in identifying targets. Things
don't always appear as you might expect.


Likewise. A missing part of this discussion is that the novice will
only be able to make marginal use of a radar. It takes some training
(at least several hours, ideally more) and a lot of practice to be
proficient. Even then, when its needed the most (in heavy fog for
instance) the helmsman it likely preoccupied doing basic navigation,
and the first watch should be ears and eyes. The only way that radar
is useful is if there is a dedicated radar watch, or if the helmsman
is quite experienced.


How far away will it detect:
1. A ship

Over 5 miles

This would be a minimum. If the radar is mounted 20 feet up (this if
often cited as the optimal height, though its open for discussion) the
radar horizon is 5 miles. Thus, an object that has a good return at
twenty feet up it theoretically visible at 10 miles, though this might
be pushing the limits of a small unit.



2. A buoy with a corner reflector

1 - 2 miles, I think.

Jeeze, you can see a larger buoy at 2.5 miles! Radar should see them
a bit further off. Usually when I first spot a distant buoy I use the
radar to tell me if that's my waypoint or just a boat.




3. A small sailboat with radar reflector

about the same

Again, the theoretical limit is about 10 miles, but in practice its
less than half that. And remember, half the reflectors are junk.



4. A small sailboat WITHOUT radar reflector

varies


Under 5 miles there should be enough metal visible to give a return,
but over that distance, you're only seeing a few feet of mast.



How does chop affect its performance?

may obscure close targets - but most sets have a "Sea Clutter" control
that should help.

Chop is not an big issue, however ...

The beam width of small radars is +-12.5 degrees. Thus, if you're
heeling 15 degrees (assuming no leveling device) you're seeing almost
nothing to windward or leeward. If you're bouncing that much, your
signal is intermittent. And if you're a powerboat at speed with the
bow raised 15 degrees, you could be blind in front!



Does bad weather affect it?

Heavy rain will show up, and may obscure targets in the rain (but it
takes _very_ heavy rain to do that.)


Yes, but the heavy rain situation is one of the times you need the radar.

Jeff,
On most power boats the radar is angled down so when the boat is
underway on plane the radar is now level.
Paul


Jeff wrote:

The beam width of small radars is +-12.5 degrees. Thus, if you're
heeling 15 degrees (assuming no leveling device) you're seeing almost
nothing to windward or leeward. If you're bouncing that much, your
signal is intermittent. And if you're a powerboat at speed with the bow
raised 15 degrees, you could be blind in front!

It certainly should be - but how do you get it at the correct angle?
We've all seen powerboats with the bow sticking way up. And, if the
powerboat slows, as it should in the fog, then the radar is pointing
down. Clearly, if the bow goes up more than 25 degrees at speed,
there is no way to have the radar work at both high and low speed.

Certainly many powerboats will be using trimtabs to stay reasonably
close to proper trim, but I'm not sure we can say "most" have their
radar at a proper angle. And of course, when that sport fisherman is
blasting down Buzzard's Bay in pea soup at 30 knots, is he really
looking at the radar?

Paul Schilter wrote:
Jeff,
On most power boats the radar is angled down so when the boat is
underway on plane the radar is now level.
Paul


Jeff wrote:

The beam width of small radars is +-12.5 degrees. Thus, if you're
heeling 15 degrees (assuming no leveling device) you're seeing almost
nothing to windward or leeward. If you're bouncing that much, your
signal is intermittent. And if you're a powerboat at speed with the
bow raised 15 degrees, you could be blind in front!

In article , Jeff
wrote:

It certainly should be - but how do you get it at the correct angle?
We've all seen powerboats with the bow sticking way up. And, if the
powerboat slows, as it should in the fog, then the radar is pointing
down. Clearly, if the bow goes up more than 25 degrees at speed,
there is no way to have the radar work at both high and low speed.

Certainly many powerboats will be using trimtabs to stay reasonably
close to proper trim, but I'm not sure we can say "most" have their
radar at a proper angle. And of course, when that sport fisherman is
blasting down Buzzard's Bay in pea soup at 30 knots, is he really
looking at the radar?

Paul Schilter wrote:
Jeff,
On most power boats the radar is angled down so when the boat is
underway on plane the radar is now level.
Paul


Jeff wrote:

The beam width of small radars is +-12.5 degrees. Thus, if you're
heeling 15 degrees (assuming no leveling device) you're seeing almost
nothing to windward or leeward. If you're bouncing that much, your
signal is intermittent. And if you're a powerboat at speed with the
bow raised 15 degrees, you could be blind in front!

Actually most XBand Radar antennas are designed for 25 degree Vertical
Beamwidths at the 3db Powerpoints, which means your have 12.5 +/-
degrees of level. If you vessel has a Pitch Angle, of more than 12.5
Degrees, your radar mounting is the least of your problems, especially
for a Powerboat.

Me

In article , Jeff
wrote:

Note that magnetron life (which is a finite resource) is not used up
by standby time.

Actually, the above is not an accurate conclusion. Magnitrons are
a special type of Vacum (sp) Tube, that use a Filiment Anode, that
is Pusled at High Voltage, to create the RF energy that makes the
Transmitter Pulses. There are specific operational time limits
on filiment life for Pulsed and nonPulsed situations. Operating a
magnitron, with just the filiments lite does degrade the life of that
filiment, and will cause it to fail. It just doen't happen as fast as
when the unit is being Pulsed with High Voltage Pulses. Operational Life
is in the range of 1000 to 2000 hours and of that time, most figure 20%
will be in Standby Mode (filiment lite/no HV Pulses). Increasing
the Standby Time will extend Operational Life, but definitly not
forever, and as the filiment ages, MultiPulse, and Frequency Drift will
become issues.


Bruce in alaska
--
add a 2 before @

I asked this question of RayMarine support a few years ago. Here's
what I asked:

"I am curious as to the lifetime of the magnetron, or any other related
components. I often leave the radar in Standby Mode to save power and
magnetron wear, but have been advised that the magnetron is heated in
standby and thus can wear out. How many hours use might I expect, and
will standby reduce wear?"

Here's the response:

"The magnetron is being heated anytime the radar is in standby. This
will not, however, significantly impact the life of the magnetron.
Actual transmit time is what really wears out the magnetron. If you
are really concerned about it, you can turn off the radar scanner by
holding the CLEAR key in for about 10 seconds. this leaves the
display energized, and available for the display of chart or data.
You can turn the scanner back on at anytime by tapping the POWER key
while on the radar mode. You will have to wait 70 seconds for the
warmup sequence to complete. In an EMERGENCY you can always bypass
the magnetron warm-up by holding in the ENTER key for 5 seconds.

"For systems installed on recreational vessels, we usually see upwards
of 12,000 hours of magnetron operation. That averages out to about 4
years of heavy use. In many cases, however, we see magnetrons last 10
years or more."

If the magnetron lasts 10000 hours, and wear is only 20% in standby
mode, then that's 50,000 hours, which is a very long time for a
recreational sailor.

Bruce in Alaska wrote:
In article , Jeff
wrote:


Note that magnetron life (which is a finite resource) is not used up
by standby time.


Actually, the above is not an accurate conclusion. Magnitrons are
a special type of Vacum (sp) Tube, that use a Filiment Anode, that
is Pusled at High Voltage, to create the RF energy that makes the
Transmitter Pulses. There are specific operational time limits
on filiment life for Pulsed and nonPulsed situations. Operating a
magnitron, with just the filiments lite does degrade the life of that
filiment, and will cause it to fail. It just doen't happen as fast as
when the unit is being Pulsed with High Voltage Pulses. Operational Life
is in the range of 1000 to 2000 hours and of that time, most figure 20%
will be in Standby Mode (filiment lite/no HV Pulses). Increasing
the Standby Time will extend Operational Life, but definitly not
forever, and as the filiment ages, MultiPulse, and Frequency Drift will
become issues.


Bruce in alaska

On Fri, 24 Jun 2005 20:05:29 GMT, Bruce in Alaska
wrote:

In article , Jeff
wrote:

Note that magnetron life (which is a finite resource) is not used up
by standby time.

Actually, the above is not an accurate conclusion. Magnitrons are
a special type of Vacum (sp) Tube, that use a Filiment Anode, that
is Pusled at High Voltage, to create the RF energy that makes the
Transmitter Pulses. There are specific operational time limits
on filiment life for Pulsed and nonPulsed situations. Operating a
magnitron, with just the filiments lite does degrade the life of that
filiment, and will cause it to fail. It just doen't happen as fast as
when the unit is being Pulsed with High Voltage Pulses. Operational Life
is in the range of 1000 to 2000 hours and of that time, most figure 20%
will be in Standby Mode (filiment lite/no HV Pulses). Increasing
the Standby Time will extend Operational Life, but definitly not
forever, and as the filiment ages, MultiPulse, and Frequency Drift will
become issues.


Bruce in alaska

The bit that's pulsed in the magnetron is the cathode at the centrer
of the gadget.
The anode surrounds it, and is the machined copper piece with the
cavities.

But Bruce has it mostly right, I reckon

Brian Whatcott

In article ,
Brian Whatcott wrote:

On Fri, 24 Jun 2005 20:05:29 GMT, Bruce in Alaska
wrote:

In article , Jeff
wrote:

Note that magnetron life (which is a finite resource) is not used up
by standby time.

Actually, the above is not an accurate conclusion. Magnitrons are
a special type of Vacum (sp) Tube, that use a Filiment Anode, that
is Pusled at High Voltage, to create the RF energy that makes the
Transmitter Pulses. There are specific operational time limits
on filiment life for Pulsed and nonPulsed situations. Operating a
magnitron, with just the filiments lite does degrade the life of that
filiment, and will cause it to fail. It just doen't happen as fast as
when the unit is being Pulsed with High Voltage Pulses. Operational Life
is in the range of 1000 to 2000 hours and of that time, most figure 20%
will be in Standby Mode (filiment lite/no HV Pulses). Increasing
the Standby Time will extend Operational Life, but definitly not
forever, and as the filiment ages, MultiPulse, and Frequency Drift will
become issues.


Bruce in alaska

The bit that's pulsed in the magnetron is the cathode at the centrer
of the gadget.
The anode surrounds it, and is the machined copper piece with the
cavities.

But Bruce has it mostly right, I reckon

Brian Whatcott

Well I hadn't had my coffe yet, yesterday and the BrainPan wasn't
operating up to speed yet.....You are correct......


Bruce in alaska
--
add a 2 before @